title: Nature of the neurotoxic membrane actions of amyloid-β on hippocampal neurons in Alzheimer's disease.
abstract: The mechanism by which amyloid-β (Aβ) produces brain dysfunction in patients with Alzheimer's disease is largely unknown. According to previous studies, Aβ might share perforating properties with gramicidin, a well-accepted membrane-disrupting peptide. Therefore, we hypothesize that the key steps leading to synaptotoxicity by Aβ and gramicidin involve peptide aggregation, pore formation, and calcium dysregulation. Here, we show that Aβ and gramicidin form aggregates enriched in β-sheet structures using electron microscopy, and Thioflavin and Congo Red staining techniques. Also, we found that Aβ and gramicidin display fairly similar actions in hippocampal cell membranes, i.e. inducing Ca(2+) entry and synaptoxicity characterized by the loss of synaptic proteins and a decrease in neuronal viability. These effects were not observed in a Ca(2+) free solution, indicating that both Aβ and gramicidin induce neurotoxicity by a Ca(2+)-dependent mechanism. Using combined perforated patch clamp and imaging recordings, we found that only Aβ produced a perforation that progressed from a small (Cl(-)-selective pore) to a larger perforation that allowed the entry of fluorescent molecules. Therefore, based on these results, we propose that the perforation at the plasma membrane by Aβ is a dynamic process that is critical in producing neurotoxicity similar to that found in the brains of AD patients.
authors.affiliation: Laboratory of Neurophysiology, Department of Physiology, University of Concepción, Concepción, Chile.
authors.forename: Fernando J
authors.initials: FJ
authors.lastname: Sepúlveda
authors.forename: Humberto
authors.initials: H
authors.lastname: Fierro
authors.forename: Eduardo
authors.initials: E
authors.lastname: Fernandez
authors.forename: Carolina
authors.initials: C
authors.lastname: Castillo
authors.forename: Robert W
authors.initials: RW
authors.lastname: Peoples
authors.forename: Carlos
authors.initials: C
authors.lastname: Opazo
authors.forename: Luis G
authors.initials: LG
authors.lastname: Aguayo
mesh_terms: D000544:Alzheimer Disease / Q000209:etiology*; D016229:Amyloid beta-Peptides / Q000378:metabolism* / Q000633:toxicity*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000502:physiology; D002462:Cell Membrane / Q000187:drug effects* / Q000378:metabolism* / Q000473:pathology / Q000648:ultrastructure; D006096:Gramicidin / Q000378:metabolism* / Q000633:toxicity*; D057809:HEK293 Cells; D006624:Hippocampus / Q000166:cytology* / Q000378:metabolism; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects; D017348:Microscopy, Electron, Scanning Transmission; D009474:Neurons / Q000166:cytology*; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D016229:Amyloid beta-Peptides; D006096:Gramicidin; D002118:Calcium
keywords: Alzheimer's disease; Aβ; Aβ toxicity; Membrane disruption; Pore formation